In general, iron casting is frequently selected to be used to build heavy equipment in a variety of industries. Cast iron and other materials have a wide range of applications and are used in pipes, machines, and automotive industry parts, to name a few. Such materials are used in making machine parts where tensile strength is critical such as internal combustion engine cylinder heads, cylinder blocks, brackets and other components. With all the benefits of using materials such as cast iron, some limitations exist when repairing machinery made of cast iron and similar materials. In large and small machines, the industry currently scraps a significant amount (millions of dollars) of iron castings having defects each year, thereby creating a need in the art for apparatuses and methods which permit repair of cracked or defective components such that the repair has high tensile strength.
Typically, traditional mechanical methods employed for the repair of components with defects either require application of too much separating load on the repaired component resulting in an increased risk of progressive damage, or the repair lacks the required tensile strength resulting in inadequate repairs. The use of threaded pins for repairing cracked structures according to conventional techniques, for example, applies a separating load to the repaired part resulting in an increase in the risk of progressive damage. Lock-N-Stitch threaded repair pins create a small drawing together load, but the strength of the repair is low (i.e., less than the tensile strength of the base material being repaired), and therefore unsatisfactory. One method, Friction Stir Processing, creates at best a very low tensile strength bond because graphite flakes in cast iron segregate and align during the process, creating a zone of weakness adjacent the repair area that reduces the joint strength. Another method, welding, generally introduces a great deal of heat over long periods of time, which results in geometric distortion, additional cracking and/or excessive hardness. Another defect repair method, brazing, can deliver a tensile strength approaching the tensile strength of the base material being repaired, but with at least two substantial limitations. First, the quality of brazing is dependent on the surface cleanliness, which may be difficult to control in industrial environments, and second, brazing requires a very large amount of heat to be added to the base material over a very long time scale which may alter the metal structure of the repaired component and leave high residual stresses, an undesirable and unsatisfactory result.
Thus, there remains a need in the art for an apparatus and method which permits repair of cracked or damaged components such that the repair has high tensile strength without unacceptable distortion of or metallurgical damage to the components.